Method of heating fluids



Feb. 8, 1938. 1.. A. MEKLER METHOD OF HEATING FLUIDS fori mal Filed Jan. 6, 1a. 2 Sheets-Sheet 1 FIG.2

I INVENTOR LEV A. MEKLER @K6J4 ATTORNE Feb. 8, 1938. A. MEKLER METHOD OF HEATING FLUIDS ori inal Filed Jan. 6, 193 2 2 Sheets-Sheet 2 w 000N007 r! BA FIG.7

INVENTOR LEV A. MEKLER BY 6g ATT'ORNE Patented Feb. 8, 1938 UNITED STATES PATENT OFFICE METHOD OF HEATING FLUIDS Application January 6, 1932, Serial No. 584,966 Renewed August 15, 1935 1 Claim.

This invention relates to the heating of fluids and particularly refers to an improved method for supplying both radiant and convection heat to any fluid undergoing treatment and particu larly to hydrocarbon oils undergoing conversion. 7

As a feature of the invention the floor, the side walls and the roof of a furnace are provided with fluid conduits adjacent thereto, thus utilizing the 10 maximum interior surface of the combustion zone as radiant-heat absorbing surfaces without subjecting the fluid conduits to the danger of overheating by direct flame impingement. This same feature of the invention, which provides fluid conduits for the transmission of radiant heat to the fluid undergoing treatment in various portions of the furnace, has the additional advantage of providing different rates of heating in said various portions of the fluid conduit so that by arranging for passage of the material undergoing treatment through the various portions of the conduit or heating element in the proper sequence any desired heating curve may be obtained. For example, the fluid may be heated gradually and at an increasing rate from a minimum temperature at the entrance of the fluid into the heating element to a maximum temperature at its discharge from the heating element or the fluid may be subjected to a high 80 rate of heating upon entrance into the heating element and may thence be subjected to a more gradual rate of heating in subsequent portions of the heating element reaching its maximum temperature, if so desired, at some point in the 35 heating element substantially remote from the point of discharge. It will be understood that numerous other heating curves of any desired type may be obtained, the foregoing being given only for the purpose of illustration.

40 The arrangement of the heating element or fluid conduits along the floor, side walls and roof of the furnace is particularly advantageous in heating two streams of fluid, under substantially the same conditions, to substantially the same 45 final temperature. This expedient of splitting the stream of fluid supplied to the heating element has been found desirable in installations where relatively large quantities of material are treated in a single furnace structure, as it per- 50 mits the use of tubes or conduits of relatively small cross-section, ordinarily employed on account of their strength relative to tube or conduits of larger cross-section, without materially increasing, or, in some cases, actually reducing ,55 the pressure drop, due to friction, through the heating element. The advantage of the heating element arrangement provided by the present invention resides in the fact that it may be easily divided into two substantially equivalent heating elements, each of which are subjected to sub- 5 stantially the same heating conditions in corresponding portions thereof, thus permitting treatment of two streams of fluid under more nearly identical conditions than is possible in ordinary types of furnaces. 10

Another advantage of the present invention resides in the location of the convection heating element in the path of combustion gases from the combustion zone of the furnace to a stack but outside the main furnace structure, thus re- ,15 placing the bridge-wall type of construction with a more economical furnace structure.

The attached diagrammatic drawings illustrate one form of furnace structure embodying the principles of the present invention. Figure 20 1 is a side elevational view of the furnace, shown substantially in cross-section. Figure 2 is a cross-sectional plan view of the same furnace and Figure 3 is a sectional elevation taken along line 3-3 in Figure 1. Figures 4, 5, 6 and '7 illus- 25 trate several types of flow which may be employed in the furnace illustrated.

Referring particularly to Figures 1, 2 and 3, the main portion of the furnace comprises a floor l, front wall 2, rear wall 3, roof 4 and side walls 5 which may be of any type of construction and ordinarily comprise refractory material such as firebrick backed by common brick or other insulating material and, if desired, encased in an outer shell of steel.

Burners 6 supply fuel such as oil, gas, pulverized solid fuel or mixture of these to the central or firing duct 40 of the firing tunnels 1, air or steam being supplied in part if desired through the burners, the remaining desired quantity of 40 fresh air being supplied, preferably after preheating, to the mouth of the firing tunnels through duct 8. Said remaining quantity of air can be supplied as primary air passing through the center passage of the tunnels 1 and/or as secondary air passing either through the upper duct 4| of the tunnel or the lower duct 42 of the tunnel or both. The distribution of the primary and the secondary air which affects the charac-Z ter of the flame produced is accomplished by means of dampers 43 and 44.

The ignited combustible materials are discharged from the firing tunnels 1 into the combustion zone 9 01 the furnace, passing toward the 55 rear wall of the furnace, upward, thence back toward the front wall 2, the combustion gases passing out of the main portion of the furnace through convection zone Hi to flue H. Any desired portion of the hot combustion gases may pass directly from flue H to stack l2 by regulation of damper I3. At least a portion or all of these gases, however, preferably pass through preheater it, wherein fresh air, introduced thereto by means of fan or blower l5 through duct l6 regulated by damper ii, is indirectly contacted with the relatively hot flue gases, thus preheating the fresh air and cooling the stack gases. The desired quantity of the air, supplied by blower l5, may pass from 'preheater I4, through duct l8, regulated by damper is, into duct 8 and thence to the firing tunnels l, where its distribution may be further regulated by dampers t3 and is, while the cooled stack combustion gases pass through flue 2d regulated by damper 2! to stack 52 and thence to the atmosphere.

The heating element employed in a furnace of this type preferably comprises a number of tubes connected in series by means of suitable return bends or headers. A radiant heating element 22 comprising tubes 23 may be located along the floor l of the furnace and that portion of the floor over which the tubes are placed is preferably depressed below the level of the firing tunnels l to protect the heating element against direct flame impingement. The tubes of the floor bank 22 preferably extend across the furnace between the side walls 5 and may be connected inseries by means of return bends 25 preferably located outside the combustion zone as illustrated in Figure 3. Side wall radiant tube banks 25 and 26 consisting of a series of tubes 23 connected in series by means of return bends 24, as illustrated in Figure 2, may be located along the upper portion of the sides 5 of the furnace and are preferably protected from direct impingement of the flame, by recessing that portion of the side walls adjacent to the tubes, as indicated in Figure 3. A radiant roof bank Z'l, of tubes 23, also preferably connected in series by means of return bends 24, as illustrated in Figure 1, may be located adjacent to the roof ll of the furnace. The tube banks 22, 25, 26 and 2f receivesubstantially radiant heat from the materials undergoing combustion in the furnace and from the radiant walls of the furnace.

Provision may also be made for imparting a portion of the heat to the fluid undergoing treatment substantially by convection.- The convection tube bank 28 is preferably located outside the main furnace structure, as illustrated in the drawings by convection zone l0, tubes 23 of said convection bank being within the path of furnace gases passing from combustion zone 9 to flue ii. The tubes of the convection bank may also be connected in series by means of suitable return bends 24, as illustrated in Figure 2.

It should be understood that theconvection bank 28 as well as the floor bank 22 and the roof bank 2! may be divided into two substantially equivalent sections, side wall bank 25 being included in one section and side wall bank 25 in the other, or that all the tubes may be connected entirely in series. This will be illustrated more clearly in connection with Figures 4, 5, 6, and 7 which will be described later. It will also be understood that one or more than one row of tubes may be utilized in any or all of the various tube banks of the furnace. This will also be more clearly illustrated with reference to Figures l, 5, 6 and 7.

Referring particularly to Figure 4, which illustrates one of the many types of flow which may be desirable for use in connection with the present invention, the stream of fluid to be heated, for example a hydrocarbon oil to be subjected to conversion conditions, may be split into two substantially equal portions A and B, prior to its introduction to the heating element. Streams A and B may first pass through convection bank 28 which is divided into two substantially equal banks 28 and 28". The streams may thence pass through lines 29 and 36 respectively, preferably placed outside of the combustion zone, into the floor radiant bank 22, which is divided into two substantially equal sections 22' and 22", stream A flowing through section 22' and stream B flowing through section 22". Streams A and B may thence pass through lines 3! and 32 respectively, also preferably placed outside of the combustion zone, stream A thence passing through the radiant side wall bank 25 and stream B passing through the radiant side wall bank 26. The streams may thence pass to the radiant roof bank 21, which is also divided into two substantially equal sections 27 and 27'', stream A passing through section 21 and stream B passing through section 21", both streams passing thence out of the furnace to be combined, if desired, outside of the furnace. 7

Referring now to Figure 5, the oil or other material to be treated may enter convection bank 26, passing through the tubes of this bank in series, thence transferring through line 33, placed preferably outside of the combustion zone, to the radiant floor bank 22, passing through the tubes of this bank in series, thence transferring through line 3| also preferably placed outside of the combustion zone, to the radiant side wall bank 25, thence through the radiant roof bank 21 and through the radiant side wall bank 26', passing through the tubes of banks 25, 2,1 and, 26 in series and thence out of the furnace to subsequent portions of the system.

Referring now to Figure 6 wherein the stream of oil or other material to be heated is divided into two substantially equal streams A and B, stream A may flow through half of the convection bank 28 which is designated as 28', thence through line 29, placed preferably outside of the combustion zone, and through half of the radiant floor bank 22, designated as 22, thence through line 3 I, also placed preferably outside of the combustion zone, through side wall radiant bank 25 and thence through half the radiant roof bank 21, which is designated as 2'! and thence out of the furnace. Stream B may pass through convection bank 28", which comprises half of convection zone 28, thence through line 30, placed preferably outside of the combustion zone, through radiant floor bank 22", which is half of bank 22,thence through line 32, placed preferably outside of the combustion zone, and through the radiant side wall bank 26 to the radiant roof bank 21, passing through half of this bank which is designated as 2?" and thence out of the furnace. It will be noted that the flow illustrated in Figure 6 is the same as that illustrated in Figure 4 except that the radiant roof bank 21 comprises two rows of tubes, the fluid of each stream flowing through first half of the lower row of tubes and thence through half the upper row of tubes in this bank.

In Figure 7 the radiant tube banks 22, 25, 26 and 21 each comprise two rows of tubes. As in Figures 4 and 6, the oil or other material to be heated is divided into two substantially equal streams A and B, which flow respectively through substantially equal portions 28' and 28" of convection bank 28, passing thence through lines 29 and 30 respectively, placed preferably outside of the combustion zone, thence through the upper row of the substantially equal portions 22' and 22" respectively of the radiant floor bank 22, thence through lines 3| and 32 respectively placed preferably outside of the combustion zone, through the outer row of tubes of side Wall convection bank 25 and through the outer row of tubes of side wall convection bank 26, streams A and B thence passing respectively through substantially equal portions of the lower row of tubes of the roof convection bank 21' and 21", thence through substantially equal portions of the upper row of tubes of convection bank 21 and 21" respectively, thence respectively through the inner row of tubes of side wall convection bank 25 and through the inner row of tubes of side wall convection bank 26, stream A thence passing through line 35 through the lower row of tubes in floor convection bank 22' and out of the furnace, while stream B passes through line 36 and thence through the lower row of tubes in floor convection bank 22" and out of the furnace;

I claim as my invention:

A method for heating hydrocarbon oils in a cracking process comprising subdividing the oil to be heated into two streams, advancing each stream through a bank of heating tubes wherein the oil is heated by convection, thence passing each stream through a bank of tubes disposed adjacent the floor of the furnace wherein the oil is subjected to radiant heat, thence advancing one of said streams through a bank of tubes adjacent one wall of the furnace and the other of said streams through a bank of tubes adjacent the opposite wall of the said furnace in each of which banks of tubes the oil is subjected to radiant heat and finally passing each stream through a bank of tubes adjacent the roof of the furnace to be subjected therein to further radiant heat treatment and thereafter combining the separate streams.

LEV A. MEKLER. 

